In one present commercial optical fiber connection practice, an optical fiber has a generally frustro-conical housing or plug applied thereto by molding technique, and a receptor housing or sleeve is fabricated with a frusto-conical passage extending axially therein and adapted for receipt of the fiber so housed and for disposition of the fiber end face in registry with an optic connection interface in the passage. The sleeve defines a companion such passage extending oppositely from the optic connection interface, whereby the sleeve is adapted for receipt of a second so housed fiber to connect two such fibers by disposing their respective end faces in registered contact at the sleeve connection interface. This optical fiber connection practice and apparatus thereof and connectors resulting therefrom are seen in a patent series including U.S. Pat. No. 4,107,242 to P. K. Runge, U.S. Pat. No. 4,264,128 to W. C. Young, and U.S. Pat. No. 4,432,604 to R. E. Schwab, all such patents being assigned to Bell Telephone Laboratories, Incorporated and incorporated herein by this reference thereto.
Single mode optical fiber connection practice, such as is attained by the foregoing, imposes critical fiber end face relation as contrasted with the lesser constraints of multimode optical fiber connection. Thus, in the single mode situation, no fiber end face spacing or separation is tolerable, i.e., the end faces of two fibers being connected must be in mutual physical contact. Further, concentricity is paramount. In typical instance, the clad fiber may be one hundred and twenty five microns in diameter, with the fiber core at five microns diameter and coaxial with the cladding. If the respective cores are misaligned concentrically by more than one-half micron, the connection does not meet desired single mode specifications and is to be rejected in quality control.
In the experience of the assignee of the present invention, in its licensed practice under the above referenced patents, various factors have been observed which lead to connectors produced and not within the noted demanding specifications. Thus, given the close dimensional tolerances as against such variables as mold matter density, curing time, collective curing of products molded successively at different times, temperature and humidity, etc., only selective ones of many produced connectors pass quality control. Typical rejection of products at the quality control stage arises from dimensional mismatch as between the sleeve frustro-conical surface and that of the fiber housing, whereby the end of the fiber housing so interferes with the frustro-conical surface of the sleeve as to abut same and have its axial movement arrested at a location spaced from the desired mutual contact interface.